On the Rock- Fragments in the Cambridge Upper Greensand, 318 



of the Elsmore mine, from the surface -deposits of which tin-ore has 

 been obtained by washing. The course of the creek is mostly through 

 a black, hard slate destitute of fossils ; but at one part, for about 

 10 chains, its bed consists of a fine-grained hard granite, with 

 numerous veins of arsenical and copper pyrites, and one solid vein of 

 tin-ore, about f in. in thickness, all of which pass from the granite 

 into the slate without any interruption or change, the passage from 

 one rock into the other being also gradual. 



The chief underlying rock of the district is a black slate ; but 

 dispersed through it are small outcrops of a rather coarse-grained 

 micaceous granite, close to one of which several veins of solid tin- 

 ore, from 1 to 4 inches thick, have been found traversing the slate 

 rock. The tin-ore disseminated through the surface-deposits has 

 been derived from these veins and from a very hard and tough 

 greenstone (diabase), which occurs in large dykes and patches in 

 various places, and is probably younger than the granite. 



In conclusion the author referred to the probability that a defi- 

 ciency of water may prove a great obstacle to the full development 

 of the tin-mining industry in this district, but stated that " it seems 

 not unlikely that the production of tin-ore from this part of Australia 

 will reach, if not surpass, that of all the old tin-mining countries 

 combined." 



3. " On the included Eock-fragments of the Cambridge Upper 

 Greensand." By W. Johnson Sollas and A. J. Jukes-Browne. 



The occurrence of numerous subangular fragments in the Upper 

 Greensand formation was so far remarkable that it had already 

 attracted the notice of two previous observers (Mr. Bonney and 

 Mr. Seeley), who had both briefly hinted at the agency of ice. While 

 ignorant of the suggestions of these gentlemen, the authors of this 

 paper had been forced to the same conclusion. A descriptive list 

 had been prepared of the most remarkable of the included fragments. 

 The infallible signs of the Upper Greensand origin consisted in 

 incrustations of PUcatula sigillum, Ostrea vesicidosa, and " Copro- 

 lite," without which, it was stated, the boulders would be undistin- 

 guishable from thoje of the overlying drift. The following gene- 

 ralizations were then put forword : — 



1. The stones are mostly subangular; some consist of friable 

 sandstones and shales, which could not have borne even a brief 

 journey over the ocean-bed. 



2. Many are of large size, especially when compared with the 

 fine silt in which they were imbedded ; the stones and silt could 

 not have been borne along by the same marine current. 



3. The stones are of various lithological characters, and might be 

 referred to granitic, schistose, volcanic and sedimentary rocks, pro- 

 bably of Silurian, Old Red Sandstone, and Carboniferous age. 



Such strata are not found in situ in the neighbourhood ; and the 

 blocks must have come from Scotland or "Wales. Numerous argu- 

 ments were adduced in favour of their Scottish derivation. 



The above considerations, that numerous rock-fragments, some of 



